1. Field of the Invention
The present invention relates to methods and apparatus for centrifugal separation, and more particularly to toroidal coil centrifugation for the separation of particles and solutes from liquids.
2. Discussion of the Prior Art
Centrifugal countercurrent chromatography has been used in high efficiency analytical separation with a variety of single and two phase systems. In separation, it has been found that the geometry of the coiled column and the acting centrifugal force field play a major role in separation.
In some of the previous teachings relating to the use of toroidal coil centrifuges (for example, see Y. Ito, U.S. Pat. No. 4,051,025, Sept. 27, 1977; Ito et al., Science 189, 999 (1975); Ito et al., Anal. Biochem. 85, 614 (1978)), the coiled column is placed in the periphery of the rotating disc structure to produce a stable centrifugal force field where particles or stationary phase of a two-phase solvent system are retained in each coil unit favored by the acting direction of the force while the mobile phase is continuously eluted through the column. One of the disadvantages of this system is the lack of mixing force of the column contents which tends to produce inefficient separations.
Another type of system, called the horizontal flow-through coil planet centrifuge (e.g., see R. L. Bowman and Y. Ito, U.S. Pat. No. 3,775,309, Nov. 27, 1973; U.S. Pat. No. 3,994,805, Nov. 30, 1976, and Y. Ito, U.S. Pat. No. 4,058,460, Nov. 15, 1977), utilizes a coiled tube which synchronously rotates around its own axis in either the same direction or the opposite direction while revolving about the central axis of the centrifuge. Thus the planetary motion of the coiled column produces a rotating or oscillating centrifugal force field with respect to the coiled column.
U.S. Pat. No. 4,714,554, issued to the present inventor on Dec. 22, 1987 and incorporated herein by reference, discloses a method and apparatus for countercurrent chromatography which has proven useful in the efficient mixing of two solvent phases and which has been shown to improve retention of a stationary phase depending on the configuration of the coiled column on the rotating holder.
However, subsequent to the development of the invention disclosed in U.S. Pat. No. 4,714,554, a need has arisen to provide satisfactory retentions of stationary phases and particles in the fluctuating acceleration field produced by an apparatus of this kind, and especially for partitions in hydrophilic solvent systems which are extremely useful for separations of peptides and other polar compounds.